• Journal of the Semiconductor & Display Technology
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• v.18 no.4
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• pp.51-56
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• 2019

LuAG:Ce(Lu₃Al₅O₁₂:Ce³⁺) nano phosphor were synthesized by applying the coprecipitation method. It is used to increase the color rendering of phosphor ceramic plate for high power LEDs and laser lighting. Internal quantum efficiency and absorption of LuAG:Ce nano phosphor are 51.5 % and 64.4 %, respectively, which is higher than the previously studied nano phosphors. The maximum absorption wavelength of this phosphor is 450 nm blue light, and the emission wavelength is 510 nm. The emission wavelength shifted to longer wavelength when the concentration of Ce increased in the heat treatment of the reducing atmosphere. Thermal quenching of LuAG nano phosphor was 70 % at 200 ℃, it was explained by their significant quenching of all raman scattering modes, implying the restriction of electron-phonon couplings caused by their defects.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.3
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• pp.194-200
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• 2020

Perylene bisimide derivatives are developed for red organic phosphor because of their advantages, such as excellent luminous efficiency and high thermal stability. Despite these advantages, they have poor solubility characteristics in organic solvents and short emission wavelength as red organic phosphor for hybrid light-emitting diodes (LEDs). In this study, we prepared terrylene bisimide using a coupling reaction and swallow-tail imide group, which has excellent solubility. The structures and properties of swallow-tail terrylene bisimide (9C) were analyzed using ¹H-nuclear magnetic resonance (¹H-NMR), Fourier-transform infrared (FT-IR), UV/Vis spectroscopy, and thermal gravimetric analysis (TGA). The maximum absorption wavelength of (9C) in the UV/Vis spectrum was 647 nm, and the maximum emission wavelength was 676 nm. In the TGA, (9C) demonstrated good thermal stability with less than 5 wt% weight loss up to 415℃. In the solubility test, (9C) has a good solubility of more than 5 wt% in chloroform and dichloromethane. When the compounds (9C) were mixed with PMMA (polymethly methacrylate), the films showed peaks at 680 nm in the PL spectra. The results verify the suitability of (9C) as a red organic phosphor for hybrid LEDs.

• Korean Journal of Optics and Photonics
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• v.35 no.3
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• pp.95-106
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• 2024

In the 21st century, white light-emitting diodes (LEDs) are widely used as backlighting for liquid crystal displays and as a light source for general illumination. However, white LEDs used in lighting often use a single yellow phosphor on top of a blue LED chip, which lacks the ability to reproduce natural colors in objects under conventional illumination accurately. Recently, researchers have been actively working on realizing high color-rendering lighting by incorporating red quantum dots to improve the spectrum in the long-wavelength band, which is deficient in conventional white LEDs. In particular, how to develop and apply remote quantum dot components to ensure long-term reliability is currently under active research. This paper introduces recent research on remote quantum dot components and the current status of developing high color-rendering lightings with them. Especially, we focus on various factors that are important to consider in optimizing the optical structure of the quantum dot components and discuss the future directions and prospects of research for high color-rendering lighting technology.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.12
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• pp.47-56
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• 2010

For a human being's smooth activity, the clean air and comfortable lighting environment are needed. The suitable lighting environment is obtained generally by making it available for being formed the bright situation easy for seeing object and the visually comfortable atmosphere. In this way, even the lighting environment was changed along with economic development. Even a light source was diversified. Thus, several kinds of new light sources such as LED, OLED, PLS, and CNT came to appear. Halogen lamp, which has low efficiency due to high color rendering among lamps of being used now, is being much used yet. However, owing to radiation of UV and IR, there are many limitations to the subject in general exhibition lighting, museum, and art museum. Accordingly, a research was performed on filter that is blocked UV and IR at the same time, by using halogen lamp that is excellent in color rendering and in life.

• Journal of Internet Computing and Services
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• v.25 no.4
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• pp.65-72
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• 2024

To faithfully represent the intention of the work in the exhibition space, lighting that provides high color reproduction like natural light is required. Thus, many lighting technologies have been introduced to improve CRI, but most of them only evaluated the general color rendering index (CRI Ra), which considers eight pastel colors. Natural light provides excellent color rendering performance for all colors, including red and blue, expressed by color rendering index of R9 and R12, but most artificial lighting has the problem that color rendering performance such as R9 and R12 is significantly lower than that of natural light. Recently, lighting technology that provides CRI at the level of natural light is required to realistically express the colors of works including primary colors but related research is very insufficient. Therefore this paper proposes exhibition hall lighting that fulfills CRI with a focus on CRI Ra, R9, and R12 based on the characteristics of natural light. First reinforcement wavelength bands for improving R9 and R12 are selected through analysis of the actual measurement SPD of natural and artificial lighting. Afterward virtual SPDs with a peak wavelength within the reinforcement wavelength band are created and then SPD combination conditions that satisfy CRI Ra≥95, R9, and R12≥90 are derived through combination simulation with a commercial LED light source. Through this, after specifying two types of light sources with 405,630nm peak wavelength that had the greatest impact on the improvement of R9 and R12, the exhibition hall lighting applied with two W/C White LEDs is designed and a control Index DB of the lighting is constructed. Afterward experiments with the proposed method showed that it was possible to achieve high CRI at the level of natural light with average CRI Ra 96.5, R9 96.2, and R12 94.0 under the conditions of illuminance (300-1,000 Lux) and color temperature (3,000-5,000K).

• Korean Journal of Materials Research
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• v.27 no.6
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• pp.312-317
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• 2017

In the construction of a white LED, the region of the red emission is a very important factor. Red light emitting materials play an important role in improving the color rendering index of commercial lighting. These materials also increase the color gamut of display products. Therefore, the development of novel phosphors with red emission and the study of color tuning are actively underway to improve product quality. In the present study, heuristic algorithms were used to search for phosphors capable of increasing the color rendering index and color gamut. Using a heuristic algorithm, the phosphors that were identified were $SrGe_4O_9:Mn^{4+}$ and $BaGe_4O_9:Mn^{4+}$. Emission spectra study confirmed that these phosphors emit light in the deep red wavelength region, which can fulfill the requirement for the improvement in color rendering index and color gamut for a white LED.

• Journal of Bio-Environment Control
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• v.9 no.4
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• pp.223-229
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• 2000

This study was conducted to analyze the opto-electric characteristics of light-emitting diodes(LED) designed for growth and morphogenesis control of transplant and to quantify the photon flux emittig from LED using a quantum sensor spectroradiometer. Difference in photon flux for blue and red LED between measured by a quantum sensor and measured by a spectroradiometer and numerically integrated was not observed. This result implies a spectroradiometer can be applied to quantify the photon flux emitting from far-red LED, which can not be measured using a quantum sensor. Since photon flux increases in proportion to wavelength, photon flux of LED modules arranged for red and far-red increased in proportion to wavelength, photon flux of LED modules arranged for red and rar-red increased gradually as the number of LED stick emitting far-red in LEd modules increased. Illumination of LED modules arranged for red and far-red decreased as the number of LED stick emitting far-red in LED modules increased. There was no difference in irradiance between LED modules arranged for red and far-red.

• Journal of The Korea Institute of Healthcare Architecture
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• v.29 no.3
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• pp.29-36
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• 2023

Purpose: The purpose of this study is to find out whether the color change of the LED light source has a significant effect on the beta wave activity of EEG in the learning state. Methods: The subjects of the experiment were 20 male and female college students between the ages of 19 and 25 who routinely perform their studies. In the created learning environment, the EEG change according to the change in the lighting color was measured while solving the Mensa thinking ability problem while sitting on a desk with LED lights installed on the top and a chair with a footrest to stabilize the legs. The light source consisted of 3 ready-made colors and 6 newly created colors. A total of 9 color light stimuli were given for 2 minutes each, and the EEG change of the subject was observed. After the experiment, the correlation was analyzed based on the mid-beta wave data recorded on the QEEG according to the color change of light and the Mensa problem score. Results: It was found that the activation of mid-beta waves was stimulated in the temporal lobes (T5, T3, T6, T4) and occipital lobes (O1, O2) of all subjects who focused on solving Mensa thinking problems. As a result of comparing the top 20% and the bottom 20% of problem solving scores, the upper group had no effect of lighting, while the lower group showed increased beta wave activity in response to color light stimulation in the order of T4, T6, and T5. Implications: It was confirmed that the color of light that activates the middle beta wave varies greatly depending on the subject's attention and learning ability, and it is judged that the color of light including the green wavelength is helpful in activating the middle beta wave in the group with low learning ability.

• Korean Journal of Optics and Photonics
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• v.35 no.5
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• pp.235-240
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• 2024

Since the coronavirus pandemic, research and application of space sterilization effects using UV light sources have been rapidly increasing. In this paper, the space-sterilization effect of UV LED light sources that can be built into indoor environmental systems or lighting devices is quantitatively analyzed through an illumination optical approach. Through this, it is possible to establish a foundation for optimizing the sterilization effect in indoor spaces in the 275±5 nm wavelength range, which is known to have excellent space-sterilization power.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.5195-5200
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• 2014

White LEDs are expected to be applied widely as a lighting system. To make white LED chips, one requires a mixture with silicon and a phosphor coating on a LED blue chip. The process of preparing a mixture with silicon using phosphor involves the use of discarded phosphor in the chip process. Reducing the costs of chip production depends on many factors, such as the mixture errors, exposure over time of silicon, and changes in the characteristics of blue chip. This paper reports the characteristics of a white LED chip manufactured through a reproduction process of derelict phosphor. This method was applicable to a real LED flashlight. A derelict phosphor chip showed similar results to a normal white chip for the degradation of cd 3.2[Cd] and 3.6[Cd], color temperature, 57[K] and 58[K], and maximum white wavelength 444.3[nm] and 449.8[nm]. These results are expected to make ea great contribution to cost reduction.